A BELT OF SUJ^-SPOTS. 185 



exists, which becomes all the more striking if we believe that Jupiter 

 was once a true sun, which has parted with most of its light and heat, 

 and is approaching the condition of a crusted globe. It would only 

 be necessary to increase the number of sun-spots in order to make a 

 continuous belt around the sun, and, when one such belt was formed, 

 it is likely that there would be another to match it on the other side 

 of the equator, for, as is well known, the regions in which the greatest 

 number of sun-spots appear lie on each side of the solar equator, and 

 any general cause which increased the absolute number of sun-spots 

 would proportionally increase the number seen in the two regions of 

 their greatest frequency. 



There are other points of resemblance between the sun and Jupiter 

 which add strength to the suggestion that the sun may now be just 

 entering upon a stage which is the precursor of the gradual loss of its 

 light and heat, and of its approach to the present condition of Jupiter. 

 Careful observation has shown that different portions of the sun rotate 

 in different times, the equatorial region moving faster than any other 

 part, and curiously enough the same peculiarity is seen in Jupiter. 

 This fact came out very clearly through the study of the great red 

 spot which made its appearance in the southern hemisphere of the 

 planet in the summer of 1878, and which has only just now faded out 

 of sight. It was found that the red spot lagged behind the equatorial 

 spots, so that the latter made a complete circuit of the planet, with 

 respect to the red spot, in about forty-four and a half days. 



It must not be overlooked, however, that belts of sun-spots, no 

 matter how numerous the spots composing them might be, would bear 

 only a superficial resemblance to the belts of Jupiter, for the latter 

 have a cloud-like appearance, while sun-spots are clearly huge chasms 

 in the photosphere. In fact, a continuous band of sun-spots, as such, 

 could not exist. But in view of the close resemblance between the 

 situation of Jupiter's belts with respect to his equator, and that of the 

 zones of sun-spots with respect to the sun's equator, it is easy to con- 

 ceive that similar causes may be concerned in the production of both 

 phenomena, the effects varying with the difference in condition of the 

 two bodies. One of these causes, which would probably be operative 

 in both cases, is the rotation of the body acting upon its fluid envelope. 

 Even on the earth we have a zone of winds and violent revolving 

 storms produced in the atmosphere on each side of the equator. On 

 Jupiter, in corresponding latitudes, we see the great belts and spots, 

 whose broken and ever-changing aspect indicates the action of tem- 

 pestuous forces in the deep and dense atmosphere of that planet of a 

 magnitude incomparably greater than anything of the kind upon the 

 earth. On the sun, still in corresponding latitudes, we have the spot- 

 zones wherein rage solar tornadoes and hurricanes, as far exceeding 

 the storms upon Jupiter as the latter exceed those upon the earth. 

 "We see, then, that in three members of the solar system — the Earth, 



